The art of color-correction


If you ever did color correction with a professional tool you will have noticed that blender missed that completely.

One needs basically two things: color-correction filters and some display to check the result.

This patch is far from making the color-correction professional (especially a plugin for color matching should be added) but it enables you to correct for the most obvious problems.

The waveform display

To judge the quality of the luminance distribution across your video signal, you can view a luma-waveform instead of the usual output display on every control monitor.

The display plots for every scanline the luminance value. The lines are all drawn on top of each other. The points get brighter if the lines cross (which is very likely with several hundred scanlines). You will understand the picture most easily if you plug an oscilloscope to the Luma-video-output of your television set. It will basically look the same.

But what is it good for?

The U/V scatter plot

To judge the quality of the color-distribution and saturation, you can also view a U/V scatter-plot.

The picture is converted to YUV-format. The U- and V-values represent the angle of the color. For pixel of the picture, one point is plotted in the display at the U and V-value-position. If several pixels happen to have the same U/V-value the pixel in the plot gets brighter. To help you understand what color is ment, a hexagram marking the extreme positions (red, magenta, blue, cyan, green, yellow) is drawn and a red cross to mark the origin.

But what is it good for?

Always: remember to activate an additional control monitor of the end result. Color calibration is a matter of taste and depends on what you want.